Distributed PV systems can be either based on DC-DC power optimizers or on DC-AC power optimizers. A DC-AC power optimizer, or in short, AC optimizer, performs maximum power point tracking (MPPT) for each PV module, which is a packaged, connected assembly of plurality of solar cells, and converts DC power to low voltage AC power. The AC outputs of multiple AC optimizers are then connected in series to match the AC voltage of the grid to be able to export power to the grid.
An example of a conventional architecture illustrated in FIG. 1 shows multiple PV modules 1-1, 1-2, . . . 1-N each connected to inputs 3-1, 3-2, . . . 3-N of respective microinverters 2-1, 2-2, . . . 2-N whose respective outputs 4-1, 4-2, . . . 4-N are then connected in parallel. In such microinverter architecture, each microinverter has an AC output voltage of the full grid voltage, and thus requires high voltage devices, which leads to high cost and low efficiency. Also, each microinverter has a high step-up ratio, which leads to low efficiency.
It is noted that throughout the description and drawings, reference “N” means an integer greater than zero to illustrate that any number of elements 1 to N are within the scope of the disclosure. Likewise, numerical terms used to describe system components, such as “first” component and “second” component, which may appear in the description or appended claims, are non-liming descriptive terms for clarity of understanding.
Another example of a conventional architecture illustrated in FIG. 2 shows multiple PV modules 1-1, 1-2, . . . 1-N each connected to respectively inputs 6-1, 6-2, . . . 6-N of respective AC optimizer, module-level inverter (MLAC), 5-1, 5-2, . . . 5-N whose respective outputs 7-1, 7-2, . . . 7-N are then connected in series to a system controller 80, which is connected to the voltage of grid 90. In each MLAC, a standard full-bridge inverter 50 is used for DC/AC power conversion. As can be seen, conventional AC optimizer technologies use an AC optimizer for each PV module adding expense due to, for example, number of components and connections needed for such implementations.